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Gentlemen, > > > Rick Jelliffe wrote: > > > The grammar-based schema languages are trying > > to interpose some type system between markup structure > > and the model, without any guarantee that their type systems > > will be any easier to map to a model than the original structures > > were. Witness XML Schemas, which is conceived in terms > > of "components" (its model) but has no analog of "component" > > in either its type system or its markup. TREX and RELAX > > seem to snuffling for diamonds in the same sandpit, with as > > much chance for success. > > I do not see either TREX or RELAX as trying to interpose a type system > between markup structure and the model (I assume you mean a > conceptual/semantic model). > In fact, this is one of the big differences in philosophy I see between > TREX and RELAX on the one hand, and W3C XML Schema on the other. What sort of "semantic model" are we talking about? The ones I am familiar with are concerned at the core with type hierarchies or at least things that look awfully alot like type hierarchies. Of course I think types can be represented in a very simple fashion i.e. any constraint defines a type, and a type is no more nor less than a constraint. > > I don't believe the use of TREX and RELAX interposes a type system > between an XML-based language and a semantic model, any more than the > use of regular expressions interposes a type-system between a > string-based language and a semantic model. > And I would say "nor any less than a regular expression interposes ..." that is to say a regular expression defines a type. Thinking of types in this way imposes no complexity on information models etc. ... another way of saying this is that the type system _defines_ the semantic model. -Jonathan
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